1. Field of the Invention
The invention relates to prefabricated structures, illustratively residential dwellings, which have a prefabricated central core and are comprised of a plurality of prefabricated floor, wall and roof members that fold inwardly about the core to produce a compact partially collapsed folded structure, which is easily transportable, and fold outwardly from the core for quick and inexpensive on-site installation.
2. Background of the Invention
Over the years, the vast majority of structures, particularly residential houses, were completely constructed on-site. Specifically, once a suitable building lot has been chosen by a prospective home owner or developer, the lot was sufficiently cleared to accommodate a suitable foundation for the home. Shortly thereafter, construction proceeded through a sequence of stages. For each stage to occur, necessary materials and skilled labor were brought to the site. For example, after the foundation was laid, the shell of the house was constructed by a team of carpenters which cut to length and appropriately nailed together a requisite number of standard dimension wooden studs, illustratively 8, 10 or 12 foot sections of 2".times.4" or 2".times.6" studs. Thereafter, exterior wall and roof sheathing, and interior sub-floors were installed using appropriately sized plywood sheets, followed by the installation of exterior siding and roof shingles. Simultaneously therewith, the windows and the heating, electrical and plumbing systems were installed by carpenters, heating contractors, electricians and plumbers, respectively. Insulation was then added to the structure followed by the installation of all the interior walls and floors. Thereafter, the necessary appliances were put in position and connected to the appropriate electrical and plumbing systems. This, in turn, was illustratively followed by all remaining interior work such as painting, wall-papering, installation of interior trim and the like and any external landscaping.
While complete on-site construction, in a manner typified by that described above, has been the predominant form of house construction, construction costs, noteably labor, have substantially increased during the past two decades to the point where a significant number of buyers can no longer afford the price of a new house.
Consequently, various alternatives have been put forth in the art aimed at providing economically priced housing. In general, these alternatives all involve prefabricating various portions of a house at a central facility or plant by resident teams of skilled labor, transporting these portions to a building site and then performing the remaining assembly work on-site. It was generally thought that by prefabricating all or a significant portion of a house, sufficient cost savings would occur so that the purchase price of the installed prefabricated house would be advantageously less than that of a similarly sized conventionally constructed house. However, for a variety of reasons, the installation cost of each of these prefabricated prior art structures was substantial and, when added to the cost of manufacture and delivery, caused the total cost of any of these prefabricated structures to exceed that of conventional construction.
One such prior art prefabricated structure is described in U.S. Pat.No. 3,501,875 (issued to J. J. de Mailly on Mar. 24, 1970). This house is comprised of a number of rooms whose walls have been prefabricated from stressed concrete. Each room is nested inside another, to form two groups of nested rooms which are then loaded onto a flat-bed truck for the shipment to a building site. During on-site installation, a crane lifts each room from its nested group and appropriately positions it on a floor which has been attached to a suitable foundation. The rooms are then attached to each other. Thereafter, a prefabricated roof is laid in place over all the positioned rooms.
A house of this type carries a significant installation cost for the following illustrative reasons. First, since wiring and plumbing cannot be run within concrete walls, this necessitates that the rooms be electrically wired and plumbed at the time of on-site installation. In addition, nesting prevents any closets from being installed in any room until after the house has been installed on-site. Furthermore, any foundation used to support this house must be sufficiently strong to support its substantial weight and is thus usually fabricated from reinforced concrete which is quite expensive. Lastly, since a prefabricated house of the type described in the '875 patent is not self-supporting, steel columns or pillars are incorporated into the walls in order to support the weight of the roof. Unfortunately, steel columns are not standard in residential construction and hence, further increase the cost of the house.
Another approach was disclosed in U.S. Pat. No. 3,348,344 (issued to L. Tatevossian on Oct. 24, 1967). There, the prefabricated house is comprised of a pre-wired and plumbed central core surrounded on each of two sides by a number of folding rooms which share a common end wall that rides along a track. Each room contains two side walls connected at one end to a respective end wall and at the other end to the central core. Each side wall has a full-height hinge which collapses the wall with accordian-like folds. For shipping, the walls and floors are all folded inwardly towards the central core, and the roof sections of the house are folded down around the folded walls. During installation, the house is first positioned on a suitable foundation. The roof sections are first raised and the floor is then extended. Thereafter, to unfold the house, each end wall is pulled outwardly on its track from the central core and is then secured in place at the end of its travel.
While the installation cost of this folding structure is less than that associated with the structure disclosed in the '875 patent, it is still too large, for the illustrative reasons indicated below, to make the house described in the '344 patent economically viable over a similarly sized conventionally constructed house. Specifically, because of the substantial weight supported by each end wall and the large amount of friction between each end wall and the track in which it rides--particularly if dirt enters the track, a substantial amount of effort is required to fully extend each end wall away from the central core. Hence, a bulldozer or other heavy equipment must be procured, usually by renting at a fairly significant cost, for use in extending these walls away from the core. Furthermore, the accordian-like folds, in the rooms surrounding the central core, prevent any closets from being located anywhere but in the central core. Consequently, this severely limits available closet space, and thus necessitates that any additional closets be constructed on-site. In addition, this house is primarily constructed from aluminum, which is a non-standard and expensive building material. While unrelated to cost, this prefabricated house possesses an additional drawback in that it has a relatively high center of gravity, which disadvantageously makes the house, when folded, readily susceptible to tipping over.